A typical radio frequency receiver is not able to determine if detected noise is thermal white noise or if the noise is due to interference from another radio frequency source. If the noise is not thermal white noise, the operation of the radio frequency receiver can be degraded due to the interference changing the level of the background noise of the radio frequency receiver by an unknown amount.
If interference noise at the radio frequency receiver of a radar altimeter causes the altimeter to indicate an erroneous altitude to the user of airborne vehicle and if the pilot is not aware that the altimeter readings are incorrect, then the airborne vehicle is more prone to be in an accident.